1. Field of the Invention
The present invention relates to simultaneous recording and reproduction apparatus wherein audiovisual signals are reproduced from a recording medium while they are recorded thereto.
2. Description of Prior Art
Video cassette recorders (VCR) are very popular in homes. A main use of home VCRs is reserve recording, and recording and reproduction of audiovisual signals are performed in the concept of time-shift.
However, when so-called timer recording is set in a home VCR, the contents of recording cannot be viewed, for example, before a time when the timer recording is completed. That is, the contents of recording cannot be viewed until the recording is completed. In order solve this problem, it is proposed in Japanese Patent laid open Publication 6-14288/1994 that the contents under recording can be viewed freely from the start before the reserve recording is completed. In this reproduction-while-recording, the contents from the start to a recording position can be viewed freely during the recording, and it is called as reproduction-while-recording.
On the other hand, for a DVD-RAM or the like, zone constant linear velocity control (ZCLV) is adopted. In ZCLV, a recording medium is divided in a plurality of areas (zones) in the radial direction, and constant angular velocity recording is performed in a zone. The revolution number is different among the zones, and it is faster at an inner zone. The ZCLV is used because the margin of recording power on recording is limited so that linear velocity has a value in a certain range.
However, the above prior art has the following problems. When an amount of data overflows in a buffer at the recording side, data to be recorded is missed. Further, in reproduction-while-recording, the rates of data write and read for a medium have to be faster than a case where only reproduction is performed. When the reproduction position catches the recording position in high speed reproduction or the like, a user cannot find it. A display image is disturbed when the reproduction position catches up the recording position.
In a recording medium wherein ZCLV or CLV control is used, the optimum revolution number depends on recording position. However, when reproduction-while-recording is performed for such a recording medium, the revolution number may be different between the recording and reproduction position, and it may be necessary to change the revolution number when recording operation is shifted to reproduction operation (or vice versa). When the revolution number is changed, it takes time for the revolution number to become stable. Thus, it takes time when the recording operation is shifted to the reproduction operation or vice versa. In order to increase the data rate so that the reproduction-while-recording is allowed, the time for the shift has to be shortened as much as possible. Therefore, when it is needed to change the revolution number when the recording operation is shifted to the reproduction operation or vice versa, the data rate in reproduction-while-recording becomes smaller, and it may cause the deterioration of image or sound quality, for example, when audiovisual signals are encoded and recorded.